The present invention relates to a road pavement crack detection system and apparatuses associated therewith and more particularly relates to a crack detection system utilizing digital imaging for obtaining and storing data concerning the crack condition of a pavement.
Cracking is the visible condition indicator most closely linked to pavement condition. Current methods do not detect cracking of the road network at the stage where early intervention would be cost effective nor attribute the incidence of cracking to a specific location (due to the small sampling). Major cost savings to authorities can be made from early intervention to seal finely cracked roads rather than waiting until the cracks develop to a more serious condition as is the case when using manual methods such as visual inspection. Finely cracked roads for instance can be sealed at a relatively low cost of $2-$4 per square meter on today""s values compared to $30-$40 per square meter where cracking has progressed to a state requiring pavement rehabilitation.
There are a number of road crack measurement systems in use world wide. They range from passive systems such as video logging to active sensors such as lasers and ultrasonics. Feasibility studies have monitored the availability and performance of these technologies and commercially available systems. The existing systems are not capable of providing sufficient crack related data such as the ability to discern cracks on pavement surfaces including chip seal surfaces, at highway speeds. The existing systems further rely on post processing with manual intervention of image data in the office which often takes days before the data is available. Authorities have determined that there is a long felt want in this field of art to provide a system capable of delivering repeatable information on pavement cracking for common types of payment surfaces. As International Standards recommend that cracking is a major indicator of pavement condition, there is a need for an objective method for assessment of the extent of cracking on the road network. As a result, research has turned to automated crack detection systems but to date, and prior to the invention disclosed herein, to the best of the applicant""s knowledge, no other trader or authority has arrived at a suitable automated system which delivers the level of results required to overcome known problems associated with present crack detection methodology. Many roads with low traffic volumes are economically designed to have a thin bituminous surface. Thin cracked surfaces are particularly vulnerable in wet weather when traffic pumps water into the road pavement leading to pavement failures which causes a roughening of the surface and decreased asset value of the roads. Pavement durability is preserved by sealing the surface well before extensive cracking appears.
Pavements such as roads, carriageways and the like are subject to heavy wear from traffic and degradation from sub-grade movement and deterioration in the pavement material itself. This necessitates regular monitoring of the pavement condition so the responsible government authority can plan maintenance programs and apply finances where it is most needed. This is a massive undertaking due to the usually extensive nature of road infrastructure. For efficient monitoring every increment of road surface must be studied across its full width in order to detect serious and also fine hairline cracks which have the potential to develop into more serious cracks posing dangers for road users. Although crack detection can be done visually by skilled personnel, it is almost impossible for visual inspections to obtain the necessary crack data for all sections of road in a particular municipality/region. The cost to do these inspections is prohibitive due to the amount of labour required and in any event such inspections suffer from the influence of human subjectivity and exposure to traffic hazards.
Another more sophisticated method of crack detection involves use of a video camera which films the road surface. The video image is then post processed to detect the severity and extent of cracking. A crack resolution of 3-5 mm is about the best that can be achieved in the prior art methods by using algorithms to do extrapolations from the data which is read.
Another method involves use of digital area scan cameras for achieving an image at high speed. The images from these cameras are prone to overlap and lack definition.
Pavement condition monitoring generally involves measurement of a roughness profile and assessment of parameters of pavement surface condition such as rutting, texture and cracking. Where cracks reach a certain size remedial surface treatments will not be an effective remedy so it is imperative that cracks are detected early and preferably when they are no larger than 1 mm.
The current manual methods of crack detection are time consuming and the extent of information gathered is limited. Manual methods are also capital intensive with poor return. There is clear need in the construction industry to arrive at more efficient ways of obtaining data concerning the condition of a pavement so that maintenance programs can be organized in the future and funds allocated.
In order to overcome the shortcomings of the prior art methods the applicant determined that a survey vehicle could be equipped with automatic crack detection and classification systems using machine vision technology. This equipment would collect pavement condition data relating to cracking in conjunction with other equipment to measure road condition parameters such as roughness and rutting.
The present invention overcomes the shortcomings of the prior art by providing a crack detection system for accumulating and storage of data relative to the condition of a pavement. The invention further provides a system for obtaining digitized images of a pavement surface and computerized means for automatically analyzing the data thereby enabling efficient monitoring of the condition of the pavement surface. The present invention further provides a lighting assembly for use with a system for monitoring the condition of a road pavement surface wherein the lighting assembly enables illumination of fine pavement detail. The present invention further provides a digital camera for use with a system for monitoring the condition of a road pavement surface wherein the camera includes an automated exposure control enabling incremental snapshots of the pavement surface whilst the camera moves at up to and around 100 km per hour relative to the pavement. The invention further provides pavement monitoring software which stores, compiles and automatically assimilates data in xe2x80x9creal timexe2x80x9d relating to pavement condition obtained from a digital camera.
In broad terms, the system comprises a data acquisition vehicle having modular system equipment contained therein and which is capable of reading the condition of a pavement when the vehicle is travelling at speeds of up to 100 km per hour. Whilst 100 km per hour is considered an appropriate speed it will be appreciated that the system has been developed to accommodate faster speeds. Data from the data acquisition vehicle is obtained via the digital camera and is processed through an image processing pipe line which resolves the images into a condition enabling data on the road surface to be read. This data is then converted into computerized reports and can be compared with previously read data to provide a comparative analysis of the condition of a particular length of pavement.
In one broad form the present invention comprises a system for obtaining, storing, comparing and analyzing data relating to the condition of a pavement surface; the system comprising;
At least one digital image acquisition means positioned relative to a pavement surface so as to capture images of the surface whilst the digital image acquisition means is moving relative to the surface,
an illumination assembly to illuminate the region from which an image is taken;
an interface between the digital image acquisition means and at least one computer
processing means in said at least one computer for processing said images to detect and classify cracks and other pavement surface features.
In another broad form the present invention comprises the system as described above, including:
a lighting assembly for illuminating a pavement surface from which digitized images are taken for storage and analysis according to the process herein described, the assembly comprising;
a light source; and
means for providing even intensity and direction of the light according to the level of exposure required by the digital image acquisition means.
In another broad form the present invention comprises the system as described above wherein the digital image acquisition means includes;
a digital camera;
said camera including a sensor, a time controlled automatic external electronic exposure which captures images of the pavement surface whether the camera is stationary or moving relative to the pavement surface and wherein the camera is responsive to reflectivity of the pavement surface.
According to a preferred embodiment, the pavement condition detection system is mounted on a vehicle allowing the digital image acquisition means to capture images of the pavement surface. The camera includes an interface for downloading images captured by the camera to a central processor which receives, stores, compares and analyzes data so as to provide via a user interface an up-to-date picture of the condition of the pavement.
In its broadest form the present invention comprises:
a system for real time capture and processing of pavement crack data comprising;
a vehicle capable of traveling at highway speeds;
means for capturing digital images of the pavement surface; and
means for processing and displaying captured data.
Preferably, the digital image acquisition means comprises a digital camera and the processing means includes computer hardware and software for processing said digital images.
In its broadest form the present invention comprises:
a system for enabling real time capture and processing of data relating to the condition of a pavement the system comprising;
a vehicle capable of traveling at highway speeds;
means in or on said vehicle for capturing pavement crack data and means for processing and storage of captured data.
Preferably, the pavement is a road surface and said means for processing and storage of captured data includes means for removal of unwanted data.
In another broad form the present invention comprises;
a system for real time capture of and processing of pavement crack data relating to the condition of a road pavement said system comprising;
a vehicle capable of travelling at highway speeds;
a digital image acquisition means for capturing images of said pavement whilst said vehicle is in motion;
processing means for receiving and anaylsing data captured by said camera and for removal of any unwanted captured data.
There are a number of attendant benefits which attach to the system according to the present invention and these include reduced risk of injury to data collection personnel, less diversion of local resources to manual data collection, reduced time losses, eliminating inconsistencies in manually collected data, confidence in comparisons from year to year and region to region, confidence in accuracy of base data used for planning and budgeting, rational basis for use of cracking data in network performance, reporting and maintenance planning, reduced time at corporate level, collating data for reporting and planning, savings over current manual data collection and savings in cost of maintenance and rehabilitation of road network.